The Inbox or any mail folder can be filtered to display only unread messages. By default, unread messages appear in bold in the message list.
In Outlook 2016, select the drop-down at the top of the message list and then select All Unread Mail.
In all versions of Outlook, select the Filter Email drop-down in the Find group on the ribbon and select Unread.
At the top of your Inbox, click in the Search Current Mailbox box.
Type: isread:no and then click Enter or click the Unread button in the Refine group on the ribbon.
Note: To switch your search to the current folder or subfolders, select the Current Folder button or the Subfolders button in the Scope group on the ribbon.
A Search folder is a folder with a pre-defined set of search criteria. The contents of your search folder will update automatically as new items that meet the criteria are received.
From your Inbox, choose the Folder tab > New Search Folder.
Select Unread mail from the Reading Mail group, then select OK.